Low damped oscillation circuit for ultra short waves



Sept. 24, 1940. H. E. HOLLMANN 2,216,011

LOW DAMPED OSCILLATION CIRCUIT FOR ULTRA SHORT WAVES Filed Oct. 8, 1938wsmumm INVENTOR. HANS ERICH HOLLMANN BY y mm/ ATTORNEY.

Patented Sept. 24, 1940 UNITED STATES PATENT OFFICE LOW DAMPEDOSGILLATION CIRCUIT FOR ULTRA SHORT WAVES tion of Germany ApplicationOctober 8, 1938, Serial No. 233,911

In Germany September 17, 1937 3 Claims.

In my parent application, Serial No. 214,435, filed June 18, 1938, thereis disclosed a lowdamped oscillatory or tuning circuit for ultrashortwaves which comprises two parallel metal discs which are disposed uponan axial conductor a certain distance apart. This circuit, which is afurther development of the circuit comprising two hemispheres facingeach other upon a common shaft or spindle, in addition to the advantageinhering in a very high natural period, offers appreciable mechanicaladvantages, especially in so far as mechanical stiffness or rigidity aswell as insensitiveness to shocks or vibrations are concerned.

The object of the present invention is to provide a low-dampedoscillation circuit which, in mechanical regard, possesses theadvantages associated with the disc circuit disclosed in my parentcopending application, supra, though in electrical regard it may beconceived to be a sphere circuit (to which the above-mentionedoscillatory circuit known in the prior art is to be regarded), and whichmay therefore be used also for stabilization of waves of longer length.

According to the invention, there is disposed between the plates of thedisc circuit built as disclosed in the parent copending application, onthe outer circumference thereof, a ring consisting of a sort of materialhaving a dielectric constant greater than unity.

Fig. 1 illustrates the basic principle underlying the construction ofsuch an oscillatory circuit. F and F denote the two discs mounted upon aspindle it between which, on the outer circumference thereof, is a ringQ consisting of a material possessing a high (ii-electric constant. Thisring concentrates the capacity of the circuit upon the outer disc zonesso that the circuit, from the electric angle, is similar in itsoperation to the sphere circuit known in the prior art. However, fromthe mechanical viewpoint the arrangement here disclosed offersappreciable advantages over what is known in the earlier art. Forinstance, the stability and ruggedness of the surfaces F d and F" may besubstantially raised by simple means over the stability of hemisphereswhich, as will be remembered, must moreover be fitted with additionalcapacity surfaces. Moreover, there are additional chances for acontinuous or steady change of the natural wave-length of the circuit,that is, good tuning.

As in the arrangements known in the art, the tuning is accomplishable byvariation of the disc spacing, there being an air-gap a between the ringQ and one of the discs which represents a series capacity in referenceto the capacity constituted by the ring Q. Inasmuch as this chance totune is but hard to be utilized because of the outer circuit elementsassociated with the circuit, for instance, tube, etc., the tuningpreferably is effected by a shift of the entire ring Q with the resultthat parts thereof project from the discs or else by a disposition asshown in Fig. 2. As can be seen by referring to Fig. 2, the ring Q issplit, and part S is either withdrawable from the rest of the ring orelse it is arranged so as to be screwed out. This latter arrangement isshown in Fig. 2, where A is the axis of rotation of part S. Byadjustment of the screw V, part S may be turned more or less far intothe space between the two discs of the oscillatory circuit so that themarginal capacity between the discs is altered.

The ring Q which is provided according to the invention may consist, forinstance, of a ceramic possessing a high dielectric constant. What isessential is that the material be free from losses in order that thefreedom from damping insured by the remainder of the circuit may not beoffset by losses in the capacity ring again. However, it is known in theart that materials are available which combine a high dielectricconstant with a practically negligible low loss factor so that thecircuit turns out to be extremely free from damping. 1

The connection of the circuit here disclosed with other circuitelements, vacuum tubes, etc., may be effected in the very same way asdisclosed in the parent copending application. Thus, in the presentinstance, it is possible to subdivide the inner conductor in order thatthe feed potential of the vacuum tubes may be applied directly by way ofthe discs. A preferred exemplified embodiment of this last-named idea,as set forth in the parent copending application, is that the centralconductor of the circuit could consist simply of central expansions orreinforcements of the opposite plates. Between the two discs there couldalso be interposed a radial median sheet. The latter most suitably isbuilt up of two laminations which are forced together, withinterposition of a thin dielectric, and to these laminations the cathodeterminals of the tube are connected. Inasmuch as it is rather difficultto ac commodate one or more oscillators between the 'two discs, thoughthis is particularly easy in the case of sphere circuits, it will benecessary for the median or central laminations to project beyond thediscs so that one or more oscillator tubes may be fitted outside uponthe disc circuit. In this instance, it is necessary to divide theinsulating capacity ring into two parts in order that the middlelaminations may be passed through the same. It is, finally also feasibleto utilize the extension of the oscillation circuit axis for the antennaor to insert the circuit to act as a bridge in a Lecher wire circuit,and this may be efiected either conductively or capacitively.

What is claimed is:

1. A low-loss oscillatory circuit comprising a pair of discs havingrelatively large flat conducting surfaces spaced parallel to one anotherand substantiall coextensive, a shaft directly connecting said discstogether, said shaft forming an inductance which, together with thecapacity between said discs, forms a resonant circuit, there beingdisposed between said discs and around the marginal area only of saiddiscs a ceramic material having a high dielectric constant, and meansfor varying the position of a portion of said dielectric material withrespect to said discs for varying the tuning of the circuit.

2. A low-loss oscillatory circuit comprising a pair of discs havingrelatively large flat conducting surfaces spaced parallel to oneanother, a shaft directly connecting said discs together, said shaftforming an inductance which, together with the capacity between saiddiscs, forms a resonant circuit, there being disposed between said discsa ring of ceramic material having low losses and igh dielectricconstant, and means for varying the position of a portion of saiddielectric material with respect to said discs for varying the tuning ofthe circuit, said ring having a stationary portion and a portion whichis movable with respect to said stationary portion, whereby the capacitybetween said discs can be changed to vary the tuning of said oscillatorycircuit.

3. An oscillatory circuit of low loss comprising a pair of suitablyspaced flat metal discs and a conductor coupling said discs together attheir centers, and a relatively narrow ring of insulating materialplaced between said discs around the edge of at least one of said discsfor concentrating the capacity of said oscillatory circuit near theedges of said discs, said ring having low loss and a high dielectricconstant, at least a portion of said ring being shiftable in positionbetween said discs for changing the capacity between said discs with aconsequent change in the tuning of said circuit.

HANS ERICH HOLLMANN.

